2 3 4 HCMV glycoprotein B nucleoside-modified mRNA vaccine elicits antibody responses with 5 greater durability and breadth than MF59-adjuvanted gB protein immunization 6 7 Short Title: Immunogenicity of next-generation HCMV gB vaccines 8 9 Cody 22 23 Abstract WC: 300 (300 max) 24 Author summary WC: 188 (200 max) 25 Main Text WC: 3,177 26 Methods WC: 3,142 2 27 Abstract:28 A vaccine to prevent maternal acquisition of human cytomegalovirus (HCMV) during pregnancy 29 is a primary strategy to reduce the incidence of congenital disease. Similarly, vaccination of 30 transplant recipients against HCMV has been proposed to prevent transplant-associated HCMV 31 morbidity. The MF59-adjuvanted glycoprotein B protein subunit vaccine (gB/MF59) is the most 32 efficacious tested to-date for both indications. We previously identified that gB/MF59 vaccination 33 elicited poor neutralizing antibody responses and an immunodominant response against gB 34 antigenic domain 3 (AD-3). Thus, we sought to test novel gB vaccines to improve functional 35 antibody responses and reduce AD-3 immunodominance. Groups of juvenile New Zealand White 36 rabbits were administered 3 sequential doses of full-length gB protein with an MF59-like squalene 37 adjuvant (analogous to clinically-tested vaccine), gB ectodomain protein (lacking AD-3) with 38 squalene adjuvant, or lipid nanoparticle (LNP)-packaged nucleoside-modified mRNA encoding 39 full-length gB. The AD-3 immunodominant IgG response following human gB/MF59 vaccination 40 was closely mimicked in rabbits, with 78% of binding antibodies directed against this region in the 41 full-length gB protein group compared to 1% and 46% in the ectodomain and mRNA-LNP-42 vaccinated groups, respectively. All vaccines were highly immunogenic with similar kinetics and 43 comparable peak gB-binding and functional antibody responses. Although gB ectodomain subunit 44 vaccination reduced targeting of non-neutralizing epitope AD-3, it did not improve vaccine-elicited 45 neutralizing or non-neutralizing antibody functions. gB nucleoside-modified mRNA-LNP-46 immunized rabbits exhibited enhanced durability of IgG binding to soluble and cell membrane-47 associated gB protein as well as HCMV-neutralizing function. Furthermore, the gB mRNA-LNP 48 vaccine enhanced breadth of IgG binding responses against discrete gB peptide residues. Finally, 49 low-magnitude gB-specific T cell activity was observed in the full-length gB protein and mRNA-50 LNP vaccine groups, though not in ectodomain-vaccinated rabbits. Altogether, these data suggest 51 that the gB mRNA-LNP vaccine candidate, aiming to improve upon the partial efficacy of gB/MF59 52 vaccination, should be further evaluated in preclinical models.
Author summary:54 Human cytomegalovirus (HCMV) is the most common infectious cause of infant birth defects, 55 resulting in permanent neurologic disability for one newborn child every hour in the United States.56 Furthermore, this virus causes significant morbidity and mortality in immune-suppressed 57 transplant recipients. Af...